This isn't a full answer. But try this. First re-select the group
with another Selection move. Also, Print the selection at each step.
If you feel the selection is wrong post on mathgroup the exact
circumstances - something others can easily verify. Here is an
excerpt from something i did once that uses All:
nb = SelectedNotebook[];
SelectionMove[nb, Previous, EvaluationCell, asf];
SelectionMove[nb, All, CellContents, asf];
SelectionMove[nb, All, Word, asf];
data = NotebookRead[nb];
When I worked with this I noticed one has to try a few things to
understand what SelectionMove is doing.